Tool Bit Connection Shaft Structure for Electric Screwdriver and Electric Screwdriver

This application claims priority to Chinese Application No. 202410491546.5, having a filing date of Apr. 23, 2024, the entire contents of which are hereby incorporated by reference.

The present invention belongs to the field of electric tool and accessory technologies, and relates to a tool bit connection shaft structure for an electric screwdriver and an electric screwdriver.

In an electric screwdriver in the prior art, a magnet is usually used to attract a bit and a screw, and when a bit with a magnet is used to connect to a shaft end, the magnetism of the bit mainly comes from a magnet disposed in a connection shaft at which the bit is mounted. To increase a magnetic attraction force of a magnet disposed inside an output shaft end and also to provide a sufficiently strong magnetic force at a distal end of a long bit, it is necessary to maximize the magnetic attraction force of the magnet disposed inside the shaft end. However, as a result, to replace the bit, a large force is required to separate the bit from the connected shaft end. For many common bits, because an exposed part is small and short, the shapes of many models make it impossible to pinch and pull out such bits. Therefore, when a tool bit is tightly attracted by a magnetic force, it may even be necessary to use pliers or another tool to separate the bit from the electric screwdriver.

The use of the foregoing manner of only increasing the magnetism of a magnet to improve a screw supporting effect inevitably brings about certain negative effects. To be specific, when a long bit is used, because a screw is relatively far away from a magnet, magnetic force performance of a tip portion of the bit is greatly reduced, or even there seems to be no presence of a magnetic attraction force. In addition, the use of a manner of only increasing the area and thickness of an embedded magnet to increase a magnetic attraction force of a tip portion of a bit is also limited. To be specific, due to limitations in the size of a machine as well as upper limits in the magnetic force and the size of a magnet, it is impossible to optimally achieve a magnetic force strength required by a user, especially when a long and thin tool bit is used. Currently, none of the common commercially available electric screwdrivers can optimally converge a magnetic force at a tip portion of a tool bit, and a magnetic force is far from enough to attract and erect a screw.

In the prior art, it is quite a compromise to arrange an annular magnet outside (near a screw) an end opening of an output shaft, or simply add a magnetic sleeve outside a bit to increase a magnetic force of a tip portion of the bit. However, both manners are not ideal in terms of costs and convenience.

In view of the foregoing reasons, there is in the market an urgent need for an electric screwdriver that can allow convenient insertion and removal of bits with small sizes and small specifications and can also make a magnetic force of a tip portion of a bit strong enough to achieve optimal effects of screw attraction and screw supporting, so that in a case that operations are performed with a single hand and a machine is turned on to rotate, a screw is kept from falling off and is attracted upright at the tip portion of the bit, especially a tip portion of a long and thin bit.

To resolve the deficiencies in the prior art, an objective of the present invention is to provide a tool bit connection shaft structure for an electric screwdriver and an electric screwdriver.

To achieve the foregoing objective, the following technical solution is adopted in the present invention.

A tool bit connection shaft structure for an electric screwdriver includes a power output shaft front section and a shaft end sleeve in cooperation with the power output shaft front section, where a magnet and a bit connecting hole are provided in the shaft end sleeve, and the power output shaft front section, the magnet, and the bit connecting hole are sequentially arranged in an axial direction of the shaft end sleeve; and the shaft end sleeve is made of a non-magnetically conductive material.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, the power output shaft front section is made of a magnetically conductive material, and an end surface of the power output shaft front section and the magnet are in contact with each other.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a single-surface end surface area of the magnet is not greater than an area of a shaft end of the power output shaft front section in contact with the magnet.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a radial cross-section of the power output shaft front section is a regular polygon, a radial cross-section of the magnet is a circle, and an opposite-side size of the regular polygon is not less than a diameter of the magnet.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a magnetic force adjustment structure is further disposed at a bit connecting end of the magnet, and the magnetic force adjustment structure is one of a gasket, a ring, or a combined structure of the gasket and the ring.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, when the magnetic force adjustment structure is a ring, the ring is a ring with an inner bevel, a right-angle ring or a ring with a cross-section being a circle, and the inner bevel is in contact with a chamfer at a tail portion of a connected bit.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, when the magnetic force adjustment structure is a combined structure of the gasket and the ring, the gasket and the ring have an integrated structure with equal outer diameters or a concentric stack structure of the gasket and the ring with equal outer diameters, and the gasket is placed between the magnet and the ring.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, when the magnetic force adjustment structure is a ring, the ring is a C-shaped ring or a closed ring structure.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, when the magnetic force adjustment structure is a closed ring structure, the closed ring structure matches the chamfer at the tail portion of the bit, and the chamfer of the bit is one of an inclined-plane chamfer or a right-angled chamfer.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a C-shaped ring is further disposed at a bit connecting end of the magnet, and an arc-shaped chamfer, a trapezoidal chamfer or a right-angled chamfer matching the C-shaped ring is disposed at a tail portion of a bit.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, the power output shaft front section is transmission-connected to a motor body by a power output shaft rear section and a speed change gearbox sequentially, and the power output shaft front section and the power output shaft rear section have a split structure or an integrated structure.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a connecting sheet made of a magnetically conductive material is further disposed between the shaft end of the power output shaft front section and the magnet.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, the shaft end sleeve is connected to the C-shaped ring by an inner annular groove.

Preferably, for the foregoing tool bit connection shaft structure for an electric screwdriver, a power output shaft rear section and the shaft end sleeve have an integrated structure and a non-magnetically conductive structure, a magnetic guiding block in contact with the magnet is disposed in the integrated structure, and the magnetic guiding block is made of a magnetically conductive material.

An electric screwdriver includes the foregoing tool bit connection shaft structure for an electric screwdriver.

Beneficial effects achieved by the present invention:

Compared with the prior art, in the present invention, a disadvantage that originally an output shaft end of an electric screwdriver is generally processed by using a magnetically conductive material being iron is changed, a manner of combining an outer sleeve made of a non-magnetically conductive material and an output shaft section made of a magnetically conductive material is used, and a magnetic guiding block is disposed at a rear portion of a magnet, to increase a quantity of magnetic lines of force that converge at a tip portion at a distal end of a bit, thereby reducing magnetic leakage, and improving a magnetic force of the tip portion of the bit.

In the present invention, the magnetic force adjustment structure may be further added between the magnet and a tool bit, so that while it is ensured that a magnetic circuit is unimpeded and a magnetic force at a tip portion of a bit is sufficient, a direct attraction force of the magnet on a conventional ordinary tool bit, especially a tool bit with a small specification, is reduced to a degree that allows comfortable insertion and removal by a user.

An original internal structure of a shaft end is changed, and a spring structure for mechanical clamping is added based on an original function of magnetically attracting a bit, so that some tool bits that require more secure clamping, for example, a hex shank drill bit, can be fastened doubly.

Meanings of reference numerals in the drawings:—shaft end sleeve;—power output shaft front section;—magnet;—gasket;—C-shaped ring;—bit connecting hole;—power output shaft rear section;—inner annular groove;—connecting sheet;—ring with an inner bevel;—right-angle ring;—ring with a cross-section being a circle; and—magnetic guiding block.

The following further describes the present invention in detail with reference to the accompanying drawings. The following embodiments are only used for describing the technical solutions of the present invention more clearly, but cannot be used to limit the scope of protection of the present invention.

As shown into, this embodiment discloses a tool bit connection shaft structure for an electric screwdriver, including a power output shaft front sectionand a shaft end sleevein cooperation with the power output shaft front section. A magnetand a bit connecting holeare provided in the shaft end sleeve, and the power output shaft front section, the magnet, and the bit connecting holeare sequentially arranged in an axial direction of the shaft end sleeve. The shaft end sleeveis made of a non-magnetically conductive material, and is configured for avoiding interference with a magnetic field emitted by the magnet. The power output shaft front sectionis made of a magnetically conductive material, and an end portion of the power output shaft front sectionand the magnetare in contact with each other. A direct contact between the magnetand a shaft end surface of the power output shaft front sectionis in a relatively ideal state. Alternatively, a thin iron sheet is provided between the magnetand the shaft end surface of the power output shaft front sectionto transfer magnetic lines of force, and is in fact equivalent to being in contact, which also belongs to the scope of protection of the present invention. The magnetin this embodiment generally has a cylindrical shape, and magnetization surfaces of the magnetare two end portions, i.e., the magnetis axially magnetized.

As shown in, as can be seen from the foregoing description, when a bit is inserted into the bit connecting hole, magnetically conductive structures exist on two sides of the magnet. In consideration of that magnetic field lines are symmetrically distributed on the two sides of the magnet. A dotted line A inrepresents a symmetry center of the magnetic field lines generated by the magnet. Because the shaft end sleevelocated outside the magnetis made of a non-magnetically conductive material, it may be considered that the shaft end sleevehas no impact (or little impact) on a distribution of a magnetic field. In addition, because the magnetically conductive structures exist on the two sides of the magnet, most magnetic field lines are distributed in the magnetically conductive structures on the two sides. In addition, the magnetically conductive structures are “stretched” along an axis, i.e., magnetic field lines inside the magnetically conductive structures extend in an axial direction of the magnetically conductive structures. For details, refer to a size DI in. If a magnetically conductive structure is provided on neither of the two sides of the magnet, it may be considered that air exists on two sides of D. Air has extremely low permeability, which can nearly be considered to be zero. In this state, the size Dinis relatively small.

To make the magnetic field lines emitted from two ends of the magnetenter the magnetically conductive structures as much as possible and avoid a “magnetic leakage” phenomenon along an outer edge of the magnet, therefore, in this embodiment, a single-surface end surface area of the magnetis not greater than an area of a shaft end of the power output shaft front sectionin contact with the magnet. Generally, a cross-section of the power output shaft front sectionis a regular polygon (during specific implementation, a regular polygon is mostly used), a radial cross-section of the magnetis a circle, and an opposite-side size (a minimum radial size) of the regular polygon is not less than a diameter of the magnet.

To resolve the problem of controlling bit insertion and removal forces mentioned in the BACKGROUND, in this embodiment, a magnetic force adjustment structure is further disposed at a bit connecting end of the magnet, and the magnetic force adjustment structure is one of a gasket, a ring, or a combined structure of the gasketand the ring.

When the magnetic force adjustment structure is a ring, the ring is a ringwith an inner bevel, a right-angle ringor a ringwith a cross-section being a circle, and the inner bevel is in contact with a chamfer at a tail portion of a connected bit.

When the magnetic force adjustment structureis a combined structure of the gasket and the ring, the gasketand the ring have an integrated structure () with equal outer diameters or a concentric stack structure (a split structure) of the gasketand the ring with equal outer diameters, and the gasketis placed between the magnetand the ring.

When the magnetic force adjustment structure is a ring, the ring is a C-shaped ringor a closed ring structure. When the magnetic force adjustment structure is a closed ring structure, the closed ring structure matches the chamfer at the tail portion of the bit, and the chamfer of the bit is one of an inclined-plane chamfer or a right-angled chamfer.

When the C-shaped ringis used, an arc-shaped chamfer (), a trapezoidal chamfer () or a right-angled chamfer () matching the C-shaped ringis disposed at a tail portion of a bit. The benefit of this design is that in one aspect, an attraction force between the bit and the magnetcan be increased through a mechanical locking force of the C-shaped ring, and moreover, the magnetic force adjustment structure is bonded between a periphery of the tail portion of the bit and the magnet, so that a magnetic flux cross-section between an outer edge of the tail portion of the bit and the magnetis larger, thereby improving the magnetoconductivity between the two. Double-dot dash lines inmay represent the distribution of the foregoing magnetic field. It can be seen that when being a magnetically conductive structure, the magnetic force adjustment structure can connect the outer edge of the tail portion of the bit and the magnet, to avoid a “magnetic leakage” phenomenon at this position.

The shaft end sleeveis connected to the C-shaped ringby an inner annular groove. The inner annular grooveis configured for fastening an axial position of the C-shaped ring. Within a specific range, it may be allowed that the C-shaped ringhas a specific radial contraction capability.

In this embodiment, the power output shaft front sectionis transmission-connected to a motor body by a power output shaft rear sectionand a speed change gearbox sequentially, and the power output shaft front sectionand the power output shaft rear sectionhave a split structure or an integrated structure. As shown in, the power output shaft rear sectionand the shaft end sleevehave an integrated structure and a non-magnetically conductive structure, a magnetic guiding blockin contact with the magnetis disposed in the integrated structure, and the magnetic guiding blockis made of a magnetically conductive material, and has the function of the power output shaft front sectionin the magnetic field.

In some application scenarios, a connecting sheetmade of a magnetically conductive material is further disposed between the shaft end of the power output shaft front sectionand the magnet.

This embodiment further discloses an electric screwdriver using the foregoing tool bit connection shaft structure for an electric screwdriver.

Compared with the prior art, in the present invention, a disadvantage that originally an output shaft end of an electric screwdriver is generally processed by using a magnetically conductive material being iron is changed, a manner of combining an outer sleeve made of a non-magnetically conductive material and an output shaft section made of a magnetically conductive material is used, and a magnetic guiding block (the magnetic guiding block and the output shaft section may be combined into one part) is disposed at a rear portion of a magnet, to increase a quantity of magnetic lines of force that converge at a tip portion at a distal end of a bit, thereby reducing magnetic leakage, and improving a magnetic force of the tip portion of the bit.

In the present invention, the magnetic force adjustment structure may be further added between the magnet and a tool bit, so that while it is ensured that a magnetic circuit is unimpeded and a magnetic force at a tip portion of a bit is sufficient, a direct attraction force of the magnet on a conventional ordinary tool bit, especially a tool bit with a small specification, is reduced to a degree that allows comfortable insertion and removal by a user.

An original internal structure of a shaft end is changed, and a spring structure for mechanical clamping is added based on an original function of magnetically attracting a bit, so that some tool bits that require more secure clamping, for example, a hex shank drill bit, can be fastened doubly.

The foregoing descriptions are merely preferred implementations of the present invention. A person of ordinary skill in the art may further make several improvements and variations without departing from the technical principle of the present invention, and the improvements and variations fall within the scope of protection of the present invention.